leaky injector or leaky check valve????

[jakerot]

OK, I have a 92 4WD 4Dr explorer with a starting problem. It only happens in the morning. first turn, stall, second turn, starts right up (the fuel pump works)

So far I have:

1) run 2 tanks with fuel injector cleaner
2) replaced fuel filter
3) replaced air filter
4) cleaned IAC
5) cleaned MAF
6) cleaned throttly body

No luck eliminating the starting problem, so yesterday I hooked up a pressure guage to my fuel rail.

Start up and runnng pressure is 32psi. When I turn the engine off, the pressure jumps to 38psi. The next morning the pressure was effectively 0psi.

So it is safe to say my fuel system has a leak.

Check valve on fuel filter?
leaky injector?
stuck fuel pressure regulator?

I smell gas on start up a little bit, but other than that I dont smell it. Exhaust fumes look and smell normal (as far as I can tell)

According to the Chiltons website, the proper fuel pressure for my truck is 39-40psi during operation and approx 30psi during idle. So it looks like the fuel pressure regulator is not the culprit.

I was told to prime my fuel pump 3 or 4 times before turing the engine over in the morning, and if that fixed my starting problem, then my problem was a faulty check valve. Priming the pump 3 times before turning the engine over did allow the engine to start right up, so now I am guessing the fuel pump check valve is the culprit.

Since the truck has good pickup and runs fine afterwards, I am assuming the fuel injectors are fine.

Can someone confirm my reasoning before I drop my fuel tank to replace the fuel pump??

Thank you all for your great help. This website rules!!

Jakerot

 

[Jason_25]

Where did you get your pressure guage? I need to do the same to mine.

 

[jakerot]

Autozone has them for $39.95.

 

[Mike 92 XLT]

Congrats, you have correctly diagnosed a bad check valve! The fact that all the pressure bled off during the night means that the check valve is bad. Furthermore, having the correct pressure at Key On/Engine Running and at Key On/Engine Off means that the fuel pressure regulator and injectors are fine.

Mike

 

[jakerot]

Thanks Mike,

This is a great website. Very informative.

Time to drop the tank!!!

rgds,

Jakerot

 

[jakerot]

Well, I dropped the tank and changed the sending unit and the engine still sputters in the morning upon first start up try. If i run the pump 3 times and then turn her over she starts up relatively smoothly. Other than that, the engine performs fine. Good pickup. relatively smooth idle.

I guess now it is time to look at the fuel injectors? I have heard people talk about "Run Rite" fuel injector cleaning system. I am thinking on trying it.

So far I have:
changed fuel filter
Installed KKM air intake
changed fuel pressure regulator
changed sending unit
cleaned upper intake
re-torqued lower intake bolts
replaced IAC valve
ran 3 bottles of fuel injector cleaner through tank

Anyone have any comments or suggestions? Thanks

Jakerot

PS, replacing the sending unit did help the starting problem a little bit. Before, it would sputter and stall upon first start in the morning. Now it sputters and then goes to idle upon first start up in the morning.